Polysilicon resistors have been widely used in conventional integrated circuit design, including for RC oscillators, current limitation resistance, ESD protect, RF post drivers, on-chip termination, impedance matching, etc. For replacement gate technology (also referred to as gate last process), the polysilicon resistor typically includes a silicide region, which exhibits lower than desirable resistivity, and accordingly requires higher than desirable area overhead. A single crystalline silicon resistor (e.g., a resistor formed in a semiconductor substrate) has been proposed to resolve this issue, however, the single crystalline silicon resistor fails to provide precise impedance matching and capacitance for analog circuits, such as radio frequency and mixed-mode circuits.
Polysilicon electronic fuses (eFuses) have been widely used in conventional memory integrated circuit design. For high-k metal gate technology, the eFuse exhibits lower than desirable resistivity due to a metal gate formed under and a silicide region formed over the polysilicon layer, and thus it may be difficult to burn-out the eFuse. Contact, via, and copper metal have been proposed to resolve this issue, however, such proposals fail to address programming voltage issues.
What is needed is a method to fabricate a resistor or eFuse device having desirable resistivity.